I want to attach the double looped cable (bottom) to the frame: it's two metres long, and isn't convenient to wrap around the D-lock, etc. Has anyone done this? Since a clip (top) can't get past the loops on the ends, the only way I can think of is to saw the clip in half and then stick it back together on the cable, but this seems a bit... dumb.
So, if understand correctly, the lock is mounted on the down tube as sketched below?
If so, you could try placing the "U" part of the D-lock in the frame mount, hold one loop of the cable on one end of the "U", wrap the cable around the seat post & up over the top tube, then back down to the D-lock & then place the locking mechanism on (also as shown in the sketch below).